Only one word describes the effect of watching Ben Affleck slowly dial down the temperature one degree at a time in "Runner Runner": Cool. Frank Sinatra cool.

He stars as sociopathic online gambling mogul Ivan Block, and if that role doesn't sound cool, you haven't seen Affleck at the controls.

Justin Timberlake costars as Richie Furst, a Princeton whiz kid, also cool. Not as cool as Block. Nor as keen on the whole sociopathic lifestyle. The money's great, but feeding enemies to the crocodiles crosses some lines.

First we're introduced to Richie's very profitable campus online gambling services, with all the money going to a good cause called tuition. After he gets on the dean's list — and not in a good way — his fortunes change. Smart guy that he is, Richie decides he can beat the online gambling odds and cover his Princeton bill. When that doesn't work, he tracks down the guy whose online operation cheated him: the legendary Ivan Block.

Great clothes, great presence, great-looking COO Rebecca Shafran (Gemma Arterton), Block is a smooth operator with great expectations when it comes to Richie. He extends an offshore offer the kid can't refuse. FBI agent Shavers (Anthony Mackie), who has made the mogul and his Costa Rican enterprise a special project, has an offer of his own.

The question is, who is bluffing whom?

My bet's on Block no matter how the movie plays out. He is one killer of a character, and Affleck plays him like a Bach concerto — every note perfectly played. Loved Affleck in "Argo" and "The Town," but this particular Machiavellian turn reminds me more of his troubled George Reeves in "Hollywoodland." Something about the set of the jaw, the seduction in the eyes.

The crime thriller is directed by Brad Furman, who has a habit of falling in love with certain characters, as he did Matthew McConaughey's back-seat attorney in "The Lincoln Lawyer." It means he tends to forget to pay enough attention to the rest. He's done it again with Block. Richie and Rebecca deserved more.

There are other challenges, primarily a spotty script by Brian Koppelman and David Levien. They have written other manipulation stories, among them the teasing "Ocean's Thirteen," and to my mind their best, the tense "Runaway Jury." But in "Runner Runner" they've gotten completely caught up in explaining the specifics.

There is what amounts to an on-screen tutorial about online gambling, with a series of news clips decrying the practice and actual computer screen demonstrations. Yawn.

They get into why Block's business is offshore, as if terms such as "illegal" and "money laundering" are new to the lexicon. They throw in Richie's dad, Harry (John Heard), a low-end poker player and a cheat, then write "fall guy" all over him.

Fortunately we do have Timberlake. He has a way of breathing life into even deadened moments. You want to watch him. But like most stars, his acting is better when the plotting is smarter. "Runner Runner" too often sends Timberlake running down a blind alley when he should be out on a scary limb or twisting in the wind, so we have something to worry about. This is billed as a crime "thriller," after all.

There are many bribes and betrayals in "Runner Runner," a few twists on trust, and some surprise appearances by Agent Shavers, whose outrage Mackie makes fun.

A little romance is a nice break from all the money stuff. I never realized how boring it is to watch someone count it, or deliver it, or receive it. Not even when cinematographer Mauro Fiore, with an Oscar for "Avatar," is shooting the rich, the impoverished and the beautiful beaches of Costa Rica with such a discerning eye.

The struggles in the movie are with the moments when life and liberty are on the line. The ones that should put you on the edge of your seat are more likely to have you glancing at your watch.

Even with Affleck doing his Rat Pack best, by the end of "Runner Runner," the chill is gone.